CN107353886B - CO is prevented to fine and close oil reservoir 2Gas channeling nano composite material and preparation method thereof - Google Patents

CO is prevented to fine and close oil reservoir 2Gas channeling nano composite material and preparation method thereof Download PDF

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CN107353886B
CN107353886B CN201710654413.5A CN201710654413A CN107353886B CN 107353886 B CN107353886 B CN 107353886B CN 201710654413 A CN201710654413 A CN 201710654413A CN 107353886 B CN107353886 B CN 107353886B
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silicon dioxide
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nano silicon
methanol
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CN107353886A (en
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刘锐
蒲万芬
杜代军
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Southwest Petroleum University
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/58—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids
    • C09K8/594—Compositions used in combination with injected gas, e.g. CO2 orcarbonated gas
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic System
    • C07F7/02—Silicon compounds
    • C07F7/08—Compounds having one or more C—Si linkages
    • C07F7/0834—Compounds having one or more O-Si linkage
    • C07F7/0836—Compounds with one or more Si-OH or Si-O-metal linkage
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
    • C07B2200/00—Indexing scheme relating to specific properties of organic compounds
    • C07B2200/11—Compounds covalently bound to a solid support

Abstract

The invention discloses a compact oil reservoir CO prevention method 2The nanometer composite material with gas channeling uses nanometer silicon dioxide as a core, and sequentially undergoes surface modification of a silane coupling agent, Michael addition reaction of methyl acrylate and amidation reaction of 3-dimethylamino propylamine, namelyObtaining the nano composite material. The preparation method comprises the following steps: s1, preparing nano silicon dioxide; s2, surface modification of nano silicon dioxide; s3, Michael addition reaction of the modified nano silicon dioxide; s4, carrying out amidation reaction on the carbomethoxy terminated nano silicon dioxide prepared in the step S3 and 3-dimethylaminopropylamine, separating, purifying and drying to obtain the nano composite material. The composite material has good dispersibility in water phase, the viscosity of base fluid is equivalent to that of water, and the composite material and CO are 2Reacting to form organic carbonate capped nano viscoelastic fluid and improve CO 2Fluidity of (2) promoting CO 2Turn to low permeability layer to expand CO 2The swept volume of the oil reservoir improves the oil gas recovery ratio of the tight oil reservoir.

Description

CO is prevented to fine and close oil reservoir 2Gas channeling nano composite material and preparation method thereof
Technical Field
The invention belongs to the field of oilfield chemistry, and particularly relates to CO prevention suitable for a compact oil reservoir 2A gas channeling nano composite material and a preparation method thereof.
Background
With the mass production of conventional reservoirs, unconventional hydrocarbon resources such as tight hydrocarbons have become important hydrocarbon resource take-over areas. Currently, improving the oil and gas recovery ratio of tight oil reservoirs is the key point of the research of vast oilfield workers. CO 2 2The flooding not only effectively solves the major problems of industrial production, emission and storage of greenhouse gases in people's life and the like, but also becomes a key technology for improving the crude oil recovery rate by gas flooding due to the unique and effective displacement mechanism, such as the principles of safe injection, good fluidity, easy miscibility and the like.
However, large amounts of conventional reservoir CO 2Flooding field tests show that CO is compared with crude oil and formation water of an oil reservoir 2Unfavourable fluidity leading to CO 2And the flow is easy to cross along the dominant channel, and a large amount of crude oil is not used. Tight reservoirs also present the dominant path for gas channeling, such as fracturing fractures or natural fractures. The fluidity control and profile improvement is CO suppression 2Effective means of channeling along high permeability zones. Use in conventional reservoirs for CO 2Chemical agents for fluidity control and profile improvement include gels (jellies), foams, and polymers, among others. However, CO based on these micro-scale reagents 2The application benefit of the mobility control and profile improvement technology in the tight oil reservoir is not obvious, and the fundamental reason is that the micro-nano scale pores of the tight oil reservoir limit the injectability of micro-scale conventional chemical reagents in porous media. Thus developing a CO suitable for tight reservoirs 2Fluidity control agent is of great significance and profound significance。
In recent years, researchers have conducted extensive research on smart materials having environmental stimuli responsiveness. In such smart materials, CO 2Trigger-responsive materials are particularly advantageous because of the trigger CO of such materials 2Has the characteristics of environmental protection, low price, no toxicity, no harm, mild critical conditions (the critical temperature is 31.3 ℃, the critical pressure is 7.38MPa) and the like. CO 2 2The surface of the trigger-responsive smart material is usually made of CO 2Responsive radical capping, e.g. amine or amidino, CO thereof 2The response mechanism is as follows:
Figure BDA0001368882170000011
on the other hand, the polymer hybrid nano material consisting of the nano core and the polymer brush can be prepared into intelligent materials with various properties. In practice, the nanocore (rigid, flexible, optical or magnetic) and the polymer brush (environmental compatibility, biodegradability or responsiveness) can be chosen with specific properties according to the needs.
At present, most of researches on silicon dioxide nano-hybrid are focused on the application of conventional oil reservoirs, and few reports are made on the research and application of the silicon dioxide nano-hybrid in unconventional reservoirs. Therefore, the application research of the nano-silicon dioxide hybrid in the compact oil reservoir opens up a new field of application of the nano-silicon dioxide hybrid.
Disclosure of Invention
An object of the present invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
It is yet another object of the present invention to address the problem of micron scale chemical reagents in CO in the prior art 2The technical problems that weak links exist in the process of improving the recovery ratio of the tight oil reservoir by flooding and the application benefit of the tight oil reservoir is not obvious are solved, and the CO is provided 2CO prevention for improving recovery ratio of tight oil reservoir by flooding 2Gas channeling silica nanocomposites.
The invention also aims to provide a preparation method of the silicon dioxide nano composite material, which has mild reaction conditions and simple process.
To achieve these objects and other advantages in accordance with the purpose of the invention, a tight reservoir CO-protection system is provided 2The nanometer composite material of gas channeling, it regards nanometer silicon dioxide as the kernel, pass silane coupling agent surface modification, methyl acrylate Michael addition reaction and 3-dimethylamino propylamine amidation reaction sequentially, get dimethylamine end capping nanometer silicon dioxide hybrid material, namely said nanometer composite material, its structural formula is as follows:
Figure BDA0001368882170000021
preferably, the molecular mass of the nanocomposite is 4.46 × 10 -17～7.39×10 -17g。
Preferably, the particle size of the nano silicon dioxide is 20-40 nm.
Preferably, the silane coupling agent is 3-aminopropyltriethoxysilane or 3-aminopropyltrimethoxysilane.
CO is prevented to preparation foretell compact oil reservoir 2A method of gas channeling a nanocomposite comprising the steps of:
s1 preparation of nano silicon dioxide
Hydrolyzing ethyl orthosilicate to prepare nano silicon dioxide, SNPs for short;
s2 surface modification of nano silicon dioxide
Adopting silane coupling agent to carry out surface modification on the nano silicon dioxide to obtain modified nano silicon dioxide, FSNPs for short;
s3 Michael addition reaction of modified nano-silica
Carrying out Michael addition reaction on the modified nano-silica and methyl acrylate to obtain methyl ester group terminated nano-silica, MA-SNPs for short;
s4 amidation reaction
Dispersing the carbomethoxy-terminated nano silicon dioxide prepared in the step S3 in methanol, and cooling in an ice salt bath; then under the condition of stirring, dropwise adding a mixed solution of 3-dimethylaminopropylamine and methanol, heating a reaction solution system to 25 ℃, and stirring at constant temperature for reaction for 48 hours; then removing unreacted raw materials and solvent by centrifugal separation and dialysis to obtain a crude product; washing the crude product with methanol, filtering, and vacuum drying the filter cake to obtain dimethylamine-terminated nano-silica hybrid material, namely the nano-composite material, DMA-SNPs for short.
Preferably, in the above method, the step S1 specifically includes the following steps:
s11, sequentially adding 200-300 ml of absolute ethyl alcohol, 7.3-21.9 g of 35% concentrated ammonia water and 2.4-5.1 g of distilled water into a three-neck flask, and quickly stirring for 30min to ensure that the solvents are uniformly mixed;
s12, rapidly adding 52.3-89.6 g of tetraethoxysilane into the mixed solvent under the condition of rapid stirring, and reacting for 24 hours at the constant temperature of 25 ℃;
and S13, cooling, performing centrifugal separation, dialyzing, removing unreacted raw materials and solvents, purifying for many times, and drying to obtain the nano silicon dioxide with the particle size of 20-40 nm.
Preferably, step S2 specifically includes the following steps:
s21, dispersing 6.0-9.8 g of nano silicon dioxide in 150ml of toluene after vacuum drying at 100 ℃ for 24h, and performing ultrasonic dispersion treatment for 30min to ensure uniform dispersion;
s22, transferring the mixed solution into a three-neck flask, adding 2.0-3.7 g of silane coupling agent, heating to 80 ℃, and slowly stirring for reaction for 30 hours;
s23, centrifugal separation, dialysis, removing unreacted raw materials and solvent, washing with methanol, vacuum-filtering, repeating for three times, and vacuum-drying filter cakes to obtain the surface-modified nano-silica.
Preferably, the step S3 specifically includes the following steps:
s31, dispersing 3.7-6.9 g of modified nano silicon dioxide in 40-60 ml of methanol, stirring for 30min, and cooling with an ice salt bath;
s32, under the condition of stirring, dropwise adding a mixed solution consisting of 18-30 ml of methyl acrylate and methanol according to a mass ratio of 1:5.5, heating a reaction solution system to 25 ℃, and reacting at a constant temperature for 48 hours;
s33, centrifugal separation, dialysis, removing unreacted raw materials and solvent, washing with methanol, vacuum-filtering, repeating for three times, and vacuum-drying filter cakes to obtain carbomethoxy terminated nano-silica.
Preferably, in the step S4, 3-dimethylaminopropylamine and methanol are mixed in a mass ratio of 1: 5.2.
More preferably, the step S4 is specifically: dispersing 4.0-6.5 g of carbomethoxy-terminated nano silicon dioxide prepared in the step S3 in 40-60 ml of methanol under magnetic stirring, transferring the mixture to a three-neck flask, magnetically stirring for 30min, and cooling with a ice salt bath; then, under the condition of stirring, dropwise adding 20-30 ml of mixed solution of 3-dimethylaminopropylamine and methanol, heating the reaction solution system to 25 ℃, and reacting at constant temperature for 48 hours; and then, carrying out centrifugal separation and dialysis to remove unreacted raw materials and solvents, washing with methanol, carrying out vacuum filtration, repeating for three times, and carrying out vacuum drying on filter cakes to obtain the dimethylamine-terminated nano silicon dioxide.
The reaction principle of the synthesis and preparation of the nano composite material is as follows:
in the formula, the molecular structural formula of the 3-aminopropyl triethoxysilane (KH550) is as follows:
the molecular structure of methyl acrylate is as follows:
Figure BDA0001368882170000043
the molecular structure of 3-dimethylaminopropylamine is as follows:
Figure BDA0001368882170000044
compared with the prior art, the invention has the beneficial effects that:
(1) the nano composite material is uniformly dispersed in the water phase to form stable colloidal particles, the viscosity of the base fluid is equivalent to that of the water phase, the base fluid is easy to pump and inject, the flow property in micro-nano pores is good, the base fluid is ensured to have good injectivity in the unconventional oil reservoir with the micro-nano pores, and the damage rate to the matrix is small;
(2) when the nanocomposite base fluid is mixed with CO 2After the displacement front of (A) is contacted, the polymer brush on the nanocomposite surface is contacted with CO 2The reaction generates carbonate, increases the hydrodynamic size of the nano composite material, and forms the organic carbonate end-capped nano viscoelastic fluid by self-assembly, thereby improving CO 2Fluidity of (2) promoting CO 2Diversion of fluid to low permeability layer to expand CO 2The swept volume of the oil reservoir is increased, and the oil gas recovery ratio of the tight oil reservoir is further improved;
(3) when CO is in the base liquid 2When the concentration of (A) is reduced or completely removed, the viscoelastic nanofluid reverts to stable colloidal particles in CO 2The existence and removal environment, the reversible conversion of the base liquid of the silicon dioxide nano composite material from stable colloidal particles to viscoelastic fluid, and the reutilization of the nano composite material is realized.
Drawings
FIG. 1, Infrared Spectrum of nanocomposite;
FIG. 2, microstructure morphology of nanocomposite of example 1;
CO of nanocomposite of FIG. 3, example 1 2Switching performance;
FIG. 4, nanocomposite assisted CO of example 1 2And improving the recovery ratio of the compact rock core.
Detailed Description
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.
Examples of preparation of nanocomposites
Example 1
CO prevention 2The preparation of the gas channeling nano composite material comprises the following steps:
(1) preparation of nano-silica
Adding 200ml of absolute ethyl alcohol, 14.6g of concentrated ammonia water (with the concentration of 35%) and 3.4g of distilled water into a 500ml three-neck flask in sequence, placing the mixed solvent in a water bath with a magnetic stirrer, and quickly stirring for 30min to ensure that the solvent is uniformly mixed; then, under the condition of rapid stirring, 74.6g of tetraethoxysilane is rapidly added into the mixed solvent, and the mixture reacts for 24 hours at the constant temperature of 25 ℃; and cooling, performing centrifugal separation, dialyzing, removing unreacted raw materials and solvents, purifying for many times, and drying to obtain nano silicon dioxide, SNPs for short, with the particle size of 20-40 nm.
(2) Surface modification of nano-silica
Weighing 7.5g of SNPs, drying for 24h under a vacuum condition at 100 ℃, dispersing in 150ml of toluene, and carrying out ultrasonic treatment for 30 min; then, transferring the mixture into a 250ml three-neck flask, adding 2.5g of 3-aminopropyltriethoxysilane (KH550), slowly stirring under magnetic stirring, heating to 80 ℃, and reacting for 30 h; and then carrying out centrifugal separation and dialysis, removing unreacted raw materials and solvents, washing with methanol, carrying out vacuum filtration for three times, and drying a filter cake in vacuum to obtain the surface-modified nano-silica, FSNPs for short.
(3) Michael addition reaction of modified nano-silica
Weighing 5.3g of FSNPs, dispersing in 50ml of methanol under the action of magnetic stirring, transferring the mixture into a 250ml three-neck flask, stirring for 30min by using magnetic force, and cooling by using an ice salt bath; then, 24ml of methyl acrylate/methanol mixed solution (mass ratio: methyl acrylate/ethanol is 1:5.5) is added dropwise in the stirring process, the mixed solution is heated to 25 ℃ and reacted for 48 hours; and then carrying out centrifugal separation and dialysis, removing unreacted raw materials and solvents, washing with methanol, carrying out vacuum filtration, repeating for three times, and drying a filter cake in vacuum to obtain carbomethoxy terminated nano silicon dioxide, namely MA-SNPs for short.
(4) Amidation reaction
Weighing 4.5g of MA-SNPs, dispersing in 50ml of methanol under the action of magnetic stirring, transferring the mixture into a 250ml three-neck flask, magnetically stirring for 30min, and cooling with a ice salt bath; then, 26ml of 3-dimethylaminopropylamine/methanol mixed solution (mass ratio: 3-dimethylaminopropylamine/methanol is 1:5.2) is added dropwise in the stirring process, the mixed solution is heated to 25 ℃ and reacted for 48 hours; and (3) performing centrifugal separation, dialyzing, removing unreacted raw materials and solvents, washing with methanol, performing vacuum filtration, repeating for three times, and drying a filter cake in vacuum to obtain dimethylamine-terminated nano silicon dioxide, namely DMA-SNPs for short.
Example 2
CO prevention 2The preparation of the gas channeling nano composite material comprises the following steps:
(1) preparation of nano-silica
Adding 300ml of absolute ethyl alcohol, 21.9g of concentrated ammonia water (with the concentration of 35%) and 5.1g of distilled water into a 500ml three-neck flask in sequence, placing the mixed solvent in a water bath with a magnetic stirrer, and quickly stirring for 30min to ensure that the solvent is uniformly mixed; then, under the condition of rapid stirring, 89.6g of tetraethoxysilane is rapidly added into the mixed solvent, and the mixture reacts for 24 hours at the constant temperature of 25 ℃; and cooling, performing centrifugal separation, dialyzing, removing unreacted raw materials and solvents, purifying for many times, and drying to obtain nano silicon dioxide, SNPs for short, with the particle size of 20-40 nm.
(2) Surface modification of nano-silica
Weighing 9.8g of SNPs, drying for 24h under a vacuum condition at 100 ℃, dispersing in 150ml of toluene, and carrying out ultrasonic treatment for 30 min; then, transferring the mixture into a 250ml three-neck flask, adding 3.7g of 3-aminopropyltriethoxysilane (KH550), slowly stirring under magnetic stirring, heating to 80 ℃, and reacting for 30 h; and then carrying out centrifugal separation and dialysis, removing unreacted raw materials and solvents, washing with methanol, carrying out vacuum filtration for three times, and drying a filter cake in vacuum to obtain the surface-modified nano-silica, FSNPs for short.
(3) Michael addition reaction of modified nano-silica
Weighing 6.9g of FSNPs, dispersing in 60ml of methanol under the action of magnetic stirring, transferring the mixture into a 250ml three-neck flask, stirring for 30min by using magnetic force, and cooling by using a ice salt bath; then, in the stirring process, 30ml of methyl acrylate/methanol mixed solution (mass ratio: methyl acrylate/ethanol is 1:5.5) is dropwise added, the mixed solution is heated to 25 ℃ and reacted for 48 hours; and then carrying out centrifugal separation and dialysis, removing unreacted raw materials and solvents, washing with methanol, carrying out vacuum filtration, repeating for three times, and drying a filter cake in vacuum to obtain carbomethoxy terminated nano silicon dioxide, namely MA-SNPs for short.
(4) Amidation reaction
Weighing 6.5g of MA-SNPs, dispersing in 60ml of methanol under the action of magnetic stirring, transferring the mixture into a 250ml three-neck flask, magnetically stirring for 30min, and cooling with a ice salt bath; then, in the stirring process, 30ml of 3-dimethylaminopropylamine/methanol mixed solution (the mass ratio of 3-dimethylaminopropylamine/methanol is 1:5.2) is added dropwise, the mixed solution is heated to 25 ℃ and reacted for 48 hours; and (3) performing centrifugal separation, dialyzing, removing unreacted raw materials and solvents, washing with methanol, performing vacuum filtration, repeating for three times, and drying a filter cake in vacuum to obtain dimethylamine-terminated nano silicon dioxide, namely DMA-SNPs for short.
Example 3
CO prevention 2The preparation of the gas channeling nano composite material comprises the following steps:
(1) preparation of nano-silica
Adding 300ml of absolute ethyl alcohol, 7.3g of concentrated ammonia water (with the concentration of 35%) and 2.4g of distilled water into a 500ml three-neck flask in sequence, placing the mixed solvent in a water bath with a magnetic stirrer, and quickly stirring for 30min to ensure that the solvent is uniformly mixed; then, under the condition of rapid stirring, 52.3g of tetraethoxysilane is rapidly added into the mixed solvent, and the mixture reacts for 24 hours at the constant temperature of 25 ℃; and cooling, performing centrifugal separation, dialyzing, removing unreacted raw materials and solvents, purifying for many times, and drying to obtain nano silicon dioxide, SNPs for short, with the particle size of 20-40 nm.
(2) Surface modification of nano-silica
Weighing 6.0g of SNPs, drying for 24h under a vacuum condition at 100 ℃, dispersing in 150ml of toluene, and carrying out ultrasonic treatment for 30 min; then, transferring the mixture into a 250ml three-neck flask, adding 2.0g of 3-aminopropyl trimethoxy silane, and reacting for 30 hours under the condition of magnetic stirring and slow stirring, wherein the temperature is raised to 80 ℃; and then carrying out centrifugal separation and dialysis, removing unreacted raw materials and solvents, washing with methanol, carrying out vacuum filtration for three times, and drying a filter cake in vacuum to obtain the surface-modified nano-silica, FSNPs for short.
(3) Michael addition reaction of modified nano-silica
Weighing 3.7g of FSNPs, dispersing in 40ml of methanol under the action of magnetic stirring, transferring the mixture into a 250ml three-neck flask, stirring for 30min by using magnetic force, and cooling by using an ice salt bath; then, 18ml of a methyl acrylate/methanol mixed solution (the mass ratio of methyl acrylate/ethanol is 1:5.5) is added dropwise during stirring, the mixed solution is heated to 25 ℃ and reacted for 48 hours; and then carrying out centrifugal separation and dialysis, removing unreacted raw materials and solvents, washing with methanol, carrying out vacuum filtration, repeating for three times, and drying a filter cake in vacuum to obtain carbomethoxy terminated nano silicon dioxide, namely MA-SNPs for short.
(4) Amidation reaction
Weighing 4.0g of MA-SNPs, dispersing in 40ml of methanol under the action of magnetic stirring, transferring the mixture into a 250ml three-neck flask, magnetically stirring for 30min, and cooling with a ice salt bath; then, in the stirring process, 20ml of 3-dimethylaminopropylamine/methanol mixed solution (the mass ratio of 3-dimethylaminopropylamine/methanol is 1:5.2) is added dropwise, the mixed solution is heated to 25 ℃ and reacted for 48 hours; and (3) performing centrifugal separation, dialyzing, removing unreacted raw materials and solvents, washing with methanol, performing vacuum filtration, repeating for three times, and drying a filter cake in vacuum to obtain dimethylamine-terminated nano silicon dioxide, namely DMA-SNPs for short.
Second, Performance testing of nanocomposites
(1) Analysis of infrared spectra
The infrared spectra of the nanocomposites prepared in the three examples are the same, see FIG. 1. It can be seen that 3430cm -1is-CONH-, -NH 2and-CH 32930cm, was used as the peak of absorption of stretching vibration -1Is of the formula-CH 2-and-CH-stretching vibration absorption peak, 1580cm -1Is a mixed bending vibration absorption peak of C-N and N-H, 1100cm -1Is located at the stretching vibration absorption peak of-Si-O-, 800cm -1The peak is a bending vibration absorption peak of-Si-O-Si-. Therefore, the molecular structures of the nano composite materials prepared by the three examples are similar, and-CONH-and-NH are successfully introduced into the composite materials 2And obtaining the dimethylamine-terminated nano silicon dioxide composite material.
(2) Micro-morphology
FIG. 2 is a scanning electron micrograph of the nanocomposite prepared in example 1. As can be seen from the figure, the average hydraulic scale of the nanocomposite is about 60nm, and the nanocomposite has a regular particle size distribution.
(3) Stability of aqueous nanocomposite solutions
The nanocomposite prepared in example 1 was dispersed in water to prepare a solution having a mass concentration of 5.0 g/L. In this process, it can be observed that the nanocomposite disperses uniformly in the aqueous phase into stable colloidal particles, the system being milky white. After the solution is kept stand for 48 hours, the water phase system has no obvious change, no macroscopic aggregate is formed, and no precipitate is generated at the bottom of the container. This indicates that the aqueous solution of nanoparticles is a stable colloidal particle.
(4) CO of nanocomposites 2Switching performance
A series of nanocomposite aqueous solutions with different concentrations, namely DMA-SNPs base solutions, were prepared from the nanocomposite prepared in example 1. Respectively measuring the content of the nano composite material aqueous solution and CO by using a Hakke rheometer 2Shear viscosity before and after action (η) 0). Using logarithmic plotting, nanocomposite water solution and CO 2Logarithmic viscosity lg (η) before and after action 0) The relationship with the log of concentration lg (c) is shown in FIG. 3. In the figure, DMA-SNPs represent the same as CO 2Aqueous nanocomposite solution before action, DMA-SNPs-CO 2Represents a group of atoms of carbon with CO 2And (3) the nano composite material aqueous solution after the action. As can be seen from the figure, the viscosity of the base fluid of DMA-SNPs is very low and almost equivalent to that of water; when CO is introduced into the base liquid 2Then, DMA-SNPs-CO 2The hydrodynamic scale of (A) is increased, and DMA-SNPs-CO is obtained under the condition of lower concentration 2Self-assembly to form a viscoelastic nanofluid. The research finds that the CO is repeatedly introduced 2Or removing the radicals by introducing airCO in liquid 2DMA-SNPs can achieve a reversible transition from colloidal particles in a steady state to viscoelastic fluids.
(5) CO enhancement by nanocomposites 2Experiment of oil displacement efficiency
Double parallel core experiment research for improving CO content of nano composite material prepared in example 1 2Oil displacement efficiency of the compact rock core. The basic parameters of the densified cores are shown in table 1.
TABLE 1 basic parameters of parallel cores
Figure BDA0001368882170000081
The experimental scheme is as follows: first of all CO is carried out 2Driving of CO 2Injecting DMA-SNPs with the pore volume of 0.25 (PV for short) after breaking through from the outlet end of the rock core; finally carrying out subsequent CO 2And driving until the outlet end does not discharge oil any more. The rate of gas injection was 0.2ml/min and the rate of nanocomposite solution injection was 0.1 ml/min. Nanocomposite assisted CO 2The injection pressure for the densified cores, the cumulative recovery factor and the injected pore volume are plotted in fig. 4. At the initial CO injection 2Stage, the injection pressure is gradually increased, the oil is produced from the core 1# and the core 2# and is influenced by the heterogeneity, and CO 2Preferentially along the high permeability layer, resulting in a large amount of crude oil remaining in the low permeability zone. CO 2 2The extraction degree of the core 1# and the core 2# after breakthrough is 32% and 28% respectively. A0.25 PV solution of DMA-SNPs was injected and the injection pressure was increased stepwise. Thus indicating that DMA-SNPs preferentially enter the high permeation layer and displace CO at the front 2The reaction produces viscoelastic nanofluid, thereby reducing CO 2Fluidity of (2) promoting CO 2Turning to and expanding CO 2Swept volume of (a). DMA-SNPs assisted CO 2The recovery rate of the low-permeability compact rock core is improved by 30 percent or more.
In conclusion, the nano composite material is dispersed in a stable colloidal particle in a water phase, and the original viscosity of the base liquid is equivalent to that of the water phase, so that the base liquid is ensured to have good injectivity in the micro-nano porous unconventional oil reservoir; when nano-compoundingMaterial base liquid and CO 2The polymer brush on the surface of the composite material is contacted with CO 2The reaction produces carbonate, increases the hydrodynamic size of the nanocomposite, and self-assembles to form a viscoelastic fluid, thereby improving CO 2Fluidity of (2) promoting CO 2Diversion of fluid to prevent CO 2Gas channeling and CO expansion 2The swept volume of the oil-gas well is particularly suitable for unconventional tight oil reservoirs, and the oil-gas recovery ratio of the tight oil reservoirs is improved.
Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (8)

1. CO is prevented to fine and close oil reservoir 2The gas channeling nano composite material is characterized in that nano silicon dioxide is taken as an inner core, and a dimethylamine-terminated nano silicon dioxide hybrid material is obtained by sequentially carrying out surface modification of a silane coupling agent, Michael addition reaction of methyl acrylate and amidation reaction of 3-dimethylamino propylamine, wherein the structural formula of the nano composite material is as follows:
Figure FDA0002163324030000011
wherein the particle size of the nano silicon dioxide is 20-40 nm, and the silane coupling agent is 3-aminopropyl triethoxysilane or 3-aminopropyl trimethoxysilane.
2. The tight reservoir of claim 1, CO-protected 2Gas channeling nanocomposite material, characterized in that said nanocomposite materialThe molecular mass of the rice composite material is 4.46 multiplied by 10 -17～7.39×10 -17g。
3. The tight reservoir of claim 1 or 2 being CO-resistant 2The preparation method of the gas channeling nano composite material is characterized by comprising the following steps of:
s1 preparation of nano silicon dioxide
Hydrolyzing ethyl orthosilicate to prepare nano silicon dioxide;
s2 surface modification of nano silicon dioxide
Carrying out surface modification on the nano silicon dioxide by adopting a silane coupling agent to obtain modified nano silicon dioxide;
s3 Michael addition reaction of modified nano-silica
Carrying out Michael addition reaction on the modified nano-silica and methyl acrylate to obtain carbomethoxy terminated nano-silica;
s4 amidation reaction
Dispersing the carbomethoxy-terminated nano silicon dioxide prepared in the step S3 in methanol, and cooling in an ice salt bath; then under the condition of stirring, dropwise adding a mixed solution of 3-dimethylaminopropylamine and methanol, heating a reaction solution system to 25 ℃, and stirring at constant temperature for reaction for 48 hours; then removing unreacted raw materials and solvent by centrifugal separation and dialysis to obtain a crude product; and washing the crude product with methanol, performing suction filtration, and drying a filter cake in vacuum to obtain the dimethylamine-terminated nano-silica hybrid material, namely the nano-composite material.
4. The tight reservoir of claim 3, CO-protected 2The method for preparing a gas channeling nanocomposite, wherein the step S1 includes the steps of:
s11, sequentially adding absolute ethyl alcohol, concentrated ammonia water with the concentration of 35% and distilled water into a three-neck flask, and stirring and mixing uniformly;
s12, rapidly adding tetraethoxysilane under the stirring condition, and reacting for 24 hours at the constant temperature of 25 ℃;
and S13, cooling, performing centrifugal separation, dialyzing, removing unreacted raw materials and solvents, purifying for many times, and drying to obtain the nano silicon dioxide.
5. The tight reservoir of claim 4, CO-protected 2The method for preparing a gas channeling nanocomposite, wherein the step S2 includes the steps of:
s21, drying the nano silicon dioxide in vacuum at 100 ℃ for 24h, dispersing the nano silicon dioxide in toluene, and uniformly dispersing the nano silicon dioxide in the toluene by ultrasonic waves;
s22, adding a silane coupling agent, heating to 80 ℃, and slowly stirring for reaction for 30 hours;
s23, centrifugal separation, dialysis, removing unreacted raw materials and solvent, washing with methanol, vacuum-filtering, repeating for three times, and vacuum-drying filter cakes to obtain the surface-modified nano-silica.
6. The tight reservoir of claim 5, CO-protected 2The method for preparing a gas channeling nanocomposite, wherein the step S3 includes the steps of:
s31, dispersing the modified nano silicon dioxide in methanol, stirring for 30min, and cooling by using an ice salt bath;
s32, under the condition of stirring, dropwise adding a mixed solution of methyl acrylate and methanol according to the mass ratio of 1:5.5, heating the reaction solution system to 25 ℃, and reacting at constant temperature for 48 hours;
s33, centrifugal separation, dialysis, removing unreacted raw materials and solvent, washing with methanol, vacuum filtering, repeating for three times, and vacuum drying to obtain carbomethoxy terminated nano-silica.
7. The tight reservoir of claim 6, CO-protected 2The preparation method of the gas channeling nanocomposite is characterized in that 3-dimethylaminopropylamine and methanol are mixed in a mass ratio of 1:5.2 in the step S4.
8. The tight reservoir of claim 7, CO-protected 2The preparation method of the gas channeling nanocomposite material is characterized in that the step S4 specifically comprises the following steps: and (4).0-6.5 g of carbomethoxy-terminated nano silicon dioxide prepared in the step S3 is dispersed in 40-60 ml of methanol under magnetic stirring, the mixture is transferred to a three-neck flask, the mixture is magnetically stirred for 30min, and the mixture is cooled by ice salt bath; then, under the condition of stirring, dropwise adding 20-30 ml of mixed solution of 3-dimethylaminopropylamine and methanol, heating the reaction solution system to 25 ℃, and reacting at constant temperature for 48 hours; and then, carrying out centrifugal separation and dialysis to remove unreacted raw materials and solvents, washing with methanol, carrying out vacuum filtration, repeating for three times, and carrying out vacuum drying to obtain the dimethylamine-terminated nano silicon dioxide.
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